The overall objective of this project is to elucidate which stimuli are critical for inducing the enzymatic changes required for a metabolic defense against neonatal cold stress, and for the normal development of homeothermy. The artificially-reared newborn rabbit will be used as an animal model to screen several stimuli thought to be important in the dramatic perinatal induction of oxidative metabolism in heart and liver homogenates. Particular attention will be given to a possible role for perinatal cold stress and increased oxygen tension in induction mechanisms. The development of hormone-sensitive adenylate cyclase is also being studied as a basis for characterizing hormonally-mediated events in metabolic thermogenesis. BIBLIOGRAPHIC REFERENCES: Aprille, June R. (1975) "Lipid Diet and Fatty Acid Oxidation in Developing Liver," J. Cell Biol. 67, 11a. Aprille, June R. and Jill Rulfs (1976) "A Convenient Neonatal Model for Developmental Studies Requiring Artificial Diets," Biol. Neonate, In Press.